Hydraulic roller lifters with titanium valves

Thought occurred to me this would be a good idea. (Can't remember if I wrote about this previously)

With any given combo of cam-lifters-springs, if you made only one change, that is,
changing out steel valves for titanium valves, your safe RPM limit would go up (safe for the valvetrain that is).

This includes hydraulic roller deals, which have definite valvespring pressure limits. So with the same valvespring
you could rev the valvetrain to a higher RPM limit with Ti valves. As a generality, this is true.

I'm interested in building a hydraulic roller engine that can reliably run at 7000 RPM with .700" valve lift.
I'm guessing you would still be limited to what, 400 lbs open spring pressure ?
Ignoring horsepower or cubic inch arguments, or cost arguments, would this valvetrain be stable ?

Now I understand that many would say to use as much valve spring pressure as you can to safeguard the valvetrain,
but my philosophy would be to use the least amount of valvespring pressure that would safely work.

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Also, is there such a thing as titanium pushrods ?

If you come up with a way to achieve those goals, please post them. I wouldn’t think that plan is realistic, but if you succeed, more power to you! Literately.

The valve weight difference is an improvement, but if it were a big deal it would have been used everywhere 20 years ago. In some engines, the best shape cannot be made in titanium (small stem to head radius, 7mm stem).

Titanium makes a good spring, to be as stiff as steel it would be much larger.

I did something similar 8 years ago -

Intake valve 75 grams
Exhaust valve 64 grams
Morel std. travel hydraulic roller lifters, 1/4 turn preload
Bullet 269/277 @ .050", .545" lift stick
360 ci
615 hp @ 7300, 8300 at the stripe

Some Chevy LS engines use that trick. They spin up over 7000 rpm with a hyd roller cam.

George Bryce from Star Racing does it with Harley Davidson engines, he applied his knowledge from winning Championship Pro stock Motorcycle , to the street, he uses special seats & a coating on the Titanium valves for street duty, BUT the Hydro Roller lifters they use are VERY good, not like the Mopar ones we can get from the aftermarket.

LSP,
Great info, thanks. Do you recall the valvespring setup specs ?

CSK,
Fascinating. By chance can you elaborate on these super-duper hydr roller lifters ?

Spend some time looking at various Chevy LS7 builds on the internet and you'll find a ton of information on hyd roller + Ti valves. That was the factory configuration on those engines so there are a ton of them in use. http://www.superchevy.com/how-to/engines-drivetrain/1809-refresh-bigger-cam-ls7-worth-661-hp

OK thanks Andy, will do.

What would you say the pressure limit is for a hydraulic roller and why? I've ran them to 8k on steel valve LS7 engines with 200 on the seat. Multiply that by the 1.8 rocker ratio how much was the lifter seeing? (200 seat is 360 to the lifter, or the same as 240 on the seat with a 1.5 rocker)

Lightweight anything on the lifter side of the valvetrain basically means nothing. Rigidity is priority.

INTMD8,
I'm fairly ignorant on the hydr roller stuff. 8000 with steel valves is impressive to me, I'm real curious
about the cam lobes on that one. Also what was the spring open pressure ?

I thought that being a hydraulic lifter automatically limits your open pressure because of the lash take-up design,
that is the limiting factor, not the roller-wheel-versus-flat-tappet factor.

What is the upper limit on open pressure for a hydraulic, 400~~450 lbs ?

IMO the only downside to a hydraulic is you would see less net valve lift than mechanical due to potential aeration of the oil. For that you would have some degree of compressibility, otherwise liquids are mostly incompressible. I think this would to some degree be compensated for by no lash.

The cam was single pattern 3705 lobes. (236/236 @.050). Twin turbo. Open was 450. thick wall 3/8 pushrod. So, not much lift, only .612. 1,340 rwhp

240 lbs. seat, 540 lbs. open